Antenna



p 1951 c. VAN ATTA 2,567,746

\ ANTENNA Filed March 5. 1946 INVENTOR.

LESTER C. VAN ATTA ATTORNEY Patented Sept. 11, 1951 ANTENNA Lester C. Van Atta, Winchester, Mass., assignor, by m'esne assignments, to the United States of America as represented by the Secretary of the Navy Application March 5, 1946, Serial No. 652,190

This invention relates to antennas for radar systems, and more particularly to means for obtaining a radiation pattern closely approximating the relationship C50 where 0 is the angle meas= ured from the axis of the radiating means.

In search radar systems it is generally desired to produce an antenna pattern which will enable a continual and simultaneous search of both near and far objects remotely disposed on the earths surface or at equal elevations relative to the antenna, without tilting the antenna. Such a pattern is known in the art as a Csc 0 distribution.

Accordingly, the primary object of this inven tion is to construct an antenna arrangement adaptable for search radar system use to provide a continual search of near and far objects.

Another object of this invention is to provide an antenna which produces (330 0 radiation pattern, wherein the angle 0 is measured with respect to the axis of directivity of the reflector and in one quadrant of a plane intersecting said axis.

Other objects and features of .the present in vention will become apparent upon a careful consideration of the detailed description when taken with the accompanying drawings in which:

Fig. 1 is a front view of the antenna showing the structural features thereof according to one embodiment of the invention; and

Fig. 2 is a cross-sectional view of Figure 1, taken along section line II-II.

Referring to the drawings, a half-=paraboloid II is placed upon horizontal ground plate I2. Wave guide horn feed I3 is constructed and 10- cated with its aperture at the focal point IA of half-paraboloid I I. A thin, narrow metallic strip I5 is placed on ground plate I2 and attached to half-paraboloid II.

The polarization of the feed at I4 is such that the electric field intensity vectors are normal to ground plate I2. Half paraboloid reflector II together with reflecting ground plane I2 produces an effective aperture when viewed from points above reflecting ground plane I2, and a 180 degree phase discontinuity in the middle of the aperture, which results in a radiation pattern 7 Claims. (Cl. 72.50-33.65)

what different antenna configuration, is presented on pages 9-99 of Principles of Radar, 2d edition, 1946, McGraw-l-Iill Book Company, Inc. The introduction of the strip I5 and the control of the position and dimensions thereof gives additional control for shaping the space radiation pattern to produce a more closely approximated C 0 coverage. The introduction of the strip I5, however, also has a marked effect on the total reflection back into the antenna feed. It is therefore necessary in the adjustment of strip l5 to compromise these two effects. If strip I5 were quite small its important effect would be on the impedance match between the antenna and the wave guide feed It. If the strip is larger the effeet on the radiation pattern becomes more important.

The invention described in the foregoing specification need not be limited to the details shown, which are considered illustrative of one embodiment of the invention. For example, the wave guide horn feed may be replaced by a flared horn, di-pole or any other conceivable radiating means. The strip I5 need not be flat, but may be cylindri- 'cal, conical, may have double curvature, or may be left out altogether. No attempt has been made to exhaust all possible variations, but the scope of the invention is defined by the appended claims.

What is claimed is:

1. A radio antenna system comprising a radiating means, a half-paraboloid reflector, a metallic ground plate positioned in a horizontal plane, said half-paraboloid being placed on said ground plate with the axis of the half-paraboloid in said ground plate, said radiating means being mounted upon said ground plate at the focus of said reflector, said antenna system being adapted to direct radiant energy along a divergent path whereby an unsymmetrical radiation pattern is produced.

2. A radio antenna system comprising a radiating means, a half-paraboloid reflector, a metallic ground plate positioned in a horizontal plane, said half-paraboloid reflector being placed on said ground plate with the axis of the paraboloid in said ground plate, and a metallic strip attachedto said ground plate and said reflector along the junction thereof, said antenna system being adapted to direct radiant energy along a divergent path whereby an unsymmetrical radiation pattern is produced.

3. An antenna system as in claim 2, in which the dimensions of said metallic junction strip are chosen with reference to the wave length of mounted upon said ground plate with the axis of said reflector lying in said ground plate, said open ended metallic Wave guidebeing mounted upon said ground plate with the open end at the focus of said reflector, the electric vectors of the energy supplied by said wave guide being directed perpendicular to said ground plate, and a metallic strip attached to said ground plate and said reflector along the junction thereoi, the' dimensions of said metallic strip being chosen with reference to the wave length. of the radie ated energy to make the combination. oil the radiation patterns from said reflector and said metallic strip produce a radiation pattern. which varies in the axial. plane of said reflector perpendicular to saidground plate substantially as the square of. the. cosecant of the angle measured from the axis of said reflector.

5.. A. radio antenna system comprising, a radi-= ating. means, a metallic ground plate positioned in a horizontalplane, a half-=paraboloid section reflector, said reflector being mounted upon said ground plate with. the axis of said reflector lying in. the ground plate, said radiating means being mounted at. the focus of said reflector, the elec.= trio vectors of the energy supplied by said radiating means being directed perpendicular to said ground plate, and a metallic strip attached to said ground plate and said reflector along the junction. thereof, the dimensions of said. metallic strip being chosen with reference to the wave length of. the radiated energy'to make the combination of radiation pattern from said. reflector and said metallic strip produce a radiation pattern which variesin the axial plane of said reflector perpendicular to said ground plate substan tially as the square of the cosecant of the. angle measured from. the axis of said reflector.

6. A radio antenna system comprising a radiating means, a metallic ground plate, a half" paraboloid section reflector, said reflector being mounted upon said ground plate With the axis of said reflector lying in said ground plate, said radiating means being located at the focus of said reflector, the electric vectors of the energy supplied by said radiating means being directed perpendicular to said ground plate, said c0nfigu ration of reflector and ground plate being adapted to produce a radiation pattern which varies in the axial plane of said reflector perpendicular to said ground plate approximately as the square of the cosecant of the angle measured from the axis oi said reflector.

'7. A radio antenna system comprising, a radiating means, a metallic ground plate, a, half paraboloid section reflector, said reflector being mounted. upon said ground plate with the axis of said reflector lying in said ground plate, said radiating means being located at the focus of said. reflector, the electric vectors of energy supplied by said radiating means being directed perpendicular to said ground plate, and a metallic strip attached to said ground plate and said reflector at the junction thereof, the dimensions of said strip being chosen with reference to the wave length of the radiated energy to produce an optimum impedance match between said re-= flector and said radiating means. 77

LESTER C. VAN ATTA REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,026,652 Ponte -4 Jam 7, 1936 2,337,324. Granqvist Dec. 21, 1943 2,407,068 Fiske et al. Sept. 3, 1946 2,436,408 Tawney Feb. 24, 1948 2,489,869 Cutler Nov. 29, 1949 2,501,070 Martinelli Mar. 21, 1950 2,512,147 Gardner June 20, 

